CLASHES between these teams have provided some of the FA Cup's most magical moments.
The first came in the 1979 Final, when Alan Sunderland sealed a memorable 3-2 for the Gunners after United had come from 2-0 down to level.
But that drama was perhaps topped in the 1999 semi-final, when a glorious Ryan Giggs goal clinched a 2-1 victory for 10-man United after Arsenal had missed a penalty.
When Alex Ferguson and Arsene Wenger were in their pomp, Arsenal v United games were unmissable as the two best teams in England battled it out for the biggest prizes.
But both clubs have been knocked off their perch in recent seasons, with Manchester City and Chelsea emerging as the dominant teams and even Spurs rising above them.
There's still something special about this fixture though and this one takes on added importance as the FA Cup probably provides both clubs with their best chance of lifting some silverware this season.
United head to the Emirates as the form side, having won all seven games since Ole Gunnar Solskjaer replaced Jose Mourinho at the helm.
Arsenal have been far more flaky, suffering a 5-1 thumping by Liverpool and losing 1-0 at West Ham before responding with an excellent 2-0 victory over Chelsea.
But they've been formidable at home all season, with only Manchester City and Spurs winning at the Emirates, and that could count for a lot.
Solskjaer's good run has to end sometime and I suspect this might be the game when he suffers defeat for the first time.
Arsenal are a best 8/5 with Betway and that looks a good shout, with United 89/50 with Marathonbet and the draw 13/5 with a few firms.
Matches involving these sides have typically seen both teams score with David De Gea and Bernd Leno keeping just a handful of clean sheets. That's why both teams to score is just 11/20 (Marathonbet) but if you double it with a Gunners win the odds stretch to 10/3 with Bet365.
Expect both managers to pick strong sides although there could be some rotation as there are league fixtures for United and Arsenal on Tuesday.
Big guns Romelu Lukaku and Alexis Sanchez could start for United and look decent value in the anytime scorer market, with the Belgian 7/4 (Boylesports) and the Chilean 12/5 (Unibet).
Arsenal's Pierre-Emerick Aubayemang heads the market for first scorer at 9/2 (Boylesport) but try stretching the odds a bit by backing another Gunners star. Aaron Ramsey, if he starts, is a tempting 10/1 with a host of firms while winger Alex Iwobi is available at 12/1.
There's not as much needle between these sides as there was in the past but it could still pay to back a few bookings. The bookies haven't priced up that market yet but you can get odds of 7/2 with Bet365 on there being a red card.
This FA Cup match between Arsenal and Manchester United will be played on Jan 25, 2019 and kick off at 19:55. Check below for our tipsters best Arsenal vs Manchester United prediction. You may also visit our dedicated betting previews section for the most up to date previews.